1. Field of the Invention
The present invention relates to a chemical mechanical polishing (CMP) composition for removing noble metals in a CMP process.
2. Description of the Related Art
There is currently a major effort in semiconductor companies, worldwide, to commercialize high dielectric constant and ferroelectric thin films in advanced DRAMs and ferroelectric random access memories (FeRAMs), respectively. These materials include BaSrTiO3 (BST) for DRAMs and PbZrTiO3 (PZT) and SrBi2Ti2O9 (SBT) for FeRAMs.
It is well known that these materials require electrodes made from noble metals or noble metal alloys such as Pt, Ir, IrO2, Ptxe2x80x94Ru, etc., and sub-micron patterning of both the noble metals and the ferroelectric films is very difficult because of the absence of volatile products for the elemental constituents. State-of-the-art dry etching processes for Pt and Ir are known to have fundamental difficulties due to the predominantly physical (not chemical) mechanism for material removal, resulting in formation of unwanted structures (sometimes called xe2x80x9cearsxe2x80x9d) at the edges of the electrodes.
Prior copending U.S. patent application Ser. No. 08/975,366 filed Nov. 20, 1997 in the names of Peter C. Van Buskirk and Peter S. Kirlin for xe2x80x9cChemical Mechanical Polishing of FeRAM Capacitors,xe2x80x9d describes the use of CMP methodology in the fabrication of ferroelectric or high permittivity sub-micron integrated capacitors, to etch noble metal films and perovskite oxide thin film layers, without the use of reactive ion etching (RIE) or similar methods. In the method of this application, a ferroelectric capacitor structure is fabricated by sequentially depositing a bottom electrode layer, a ferroelectric layer and a top electrode layer on a base structure, optionally with deposition of a layer of a conductive barrier material beneath the bottom electrode layer, to form a capacitor precursor structure. This capacitor precursor structure is planarized by chemical mechanical polishing to yield the ferroelectric capacitor structure, e.g., a stack capacitor or trench capacitor. The process is carried out without dry etching of the electrode layers or dry etching of the ferroelectric layer, to yield ferroelectric capacitors having a very small feature size, as for example between 0.10 and 0.20 xcexcm.
In addition to the absence of the undesirable dry etching methods, other advantages of the CMP approach of this pending patent application include fewer mask levels, fewer process steps, and an inherently planarized capacitor structure that facilitates subsequent metallization.
The art continues to seek new CMP techniques and compositions for carrying out CMP processes.
There is especially a need for providing CMP techniques and compositions that are particularly adapted for removal of noble metal films such as are employed in the fabrication of electrode structures for semiconductor devices.
It therefore is an object of the present invention to provide improved CMP techniques and compositions.
It is another object of the invention to provide improved CMP techniques and compositions suitable for selective removal of noble metals and noble metal alloys, e.g., of gold, platinum, iridium, etc. from semiconductor device structures having such noble metal-based materials deposited on or otherwise present in the device structure.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.
The present invention relates to a CMP composition suitable for selective removal of noble metals and noble metal alloys from semiconductor device structures having such noble metal-based materials deposited on the device structure.
In one aspect, the invention relates to an aqueous polishing slurry composition, for use in a chemical mechanical polishing process to remove noble metal and/or noble metal alloy from a substrate having said noble metal and/or noble metal alloy deposited on the substrate, comprising:
abrasive polishing particles;
a bromide compound;
a bromate compound; and
an organic acid.
The bromate compound as employed in the CMP polishing slurry composition of the present invention provides free bromine as an oxidizing agent in the composition. It is preferred that the bromate compound exists in the slurry composition in an amount less than the bromide compound.
The organic acid as employed in the CMP polishing slurry composition of the present invention mediates decomposition of the bromate compound in the composition.
In a particular compositional embodiment, the chemical mechanical polishing composition of the invention has the following composition by weight, based on the total weight (100%) of the composition:
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.